The present invention relates to a display apparatus, particularly a color display apparatus, and a process for producing the display apparatus. More specifically, the present invention relates to a display apparatus including an electrode plate provided with a masking member improved in various properties (particularly optical properties) and productivity, and a process for production of the display apparatus.
Heretofore, a color display apparatus using a CRT (cathode-ray tube) has generally been used.
In recent years, however, various color liquid crystal apparatus have attracted considerable attention as a color display apparatus replacing the above CRT display apparatus.
FIG. 1 shows an example of such color liquid crystal apparatus.
Referring to FIG. 1, a liquid crystal display apparatus 1 includes a liquid crystal panel P and a backlight unit B.
The liquid crystal panel P includes a pair of glass substrates disposed opposite to and in parallel with each other and comprising a first (upper) glass substrate 3 and a second glass (lower) substrate 2. The second (lower) glass substrate 2 is provided with color filters (i.e., color filter segments) 5 of primary colors (red (R), green (G) and blue (B)) disposed with prescribed spacings at which a masking (light-interrupting) film 6 comprising a metal such as chromium (Cr) is disposed. The color filters 5 and the masking film 6 are covered with a protective film 7 on which a multiplicity of stripe-shaped (transparent) electrodes 9 are formed to prepare a second electrode plate. On the other hand, the first (upper) glass substrate 3 is also provided with a multiplicity of stripe-shaped (transparent) electrodes 10 disposed perpendicular to the stripe-shaped electrodes 9 to prepare a first electrode plate. These first and second glass substrates 3 and 2 (electrode plates) are applied to each other via a liquid crystal layer 11.
The color filters 5 may be formed by using processes including a dyeing process, a pigment-dispersion process and a combination of a sputtering process and a photolithographic process. The masking film 6 may be formed through a sputtering process and a subsequent photolithographic process.
On the back side of the liquid crystal panel P, a backlight unit (illumination means) for illuminating the liquid crystal panel P is disposed so as to face the first glass substrate 3 as shown in FIG. 1.
When the liquid crystal panel P is driven, liquid crystal molecules of the liquid crystal layer 11 are caused to effect switching for each pixel. Further, when the backlight unit B is driven (actuated), the liquid crystal panel P is illuminated with light issued from the backlight unit B (hereinbelow, referred to as xe2x80x9cbacklight or illuminating lightxe2x80x9d), whereby transmitted light fluxes of the backlight (illuminating light) provide various information as color display images depending on combinations thereof with the color filter segments through which the backlight passes. Between the spacings of the color filter segments of the color filter 5, the masking film 6 is disposed as mentioned above, whereby it is possible to prevent mixing of the primary colors to improve a contrast.
However, the above liquid crystal apparatus was accompanied with a problem such that light issued from a viewer side indicated as xe2x80x9cAxe2x80x9d in FIG. 1 (hereinbelow, referred to as xe2x80x9cexternal lightxe2x80x9d illuminating the panel in a direction opposite to that of the backlight) was reflected by the masking film 6 to lower a display quality of the liquid crystal panel P.
In order to solve the problem, the use of a masking film 16 or 26 (as shown in FIG. 2A or 2B) having a lamination structure comprising two or three layers has been proposed in, e.g., Japanese Laid-Open Patent Application (JP-A) 2-144525 and 61-235819. Referring to FIG. 2A, the masking film 16 includes a first layer 16a consisting of a metal (chromium) film disposed on the second substrate 2 and a second layer 16b consisting of a metal oxide (chromium oxide) film disposed on the first layer 16a. Similarly, referring to FIG. 2B, the masking film 26 has a lamination structure including a second layer 26b consisting of a metal (chromium) film disposed between first and third layers 26a and 26c each consisting of a metal oxide (chromium oxide) film. These masking films 16 and 26 are designed to retain a good display quality by the metal oxide film(s) (the first and third layers 16a, 26a and 26c) effective in decreasing a degree of the reflection of the external light and to ensure a sufficient light-interrupting property.
These masking films 16 and 26 are generally formed through a sputtering process. In the sputtering process, in case where a batch-type sputtering apparatus, it is necessary to adopt different sputtering conditions for forming the metal film and the metal oxide film. For this purpose, there has been used several methods including: (i) one wherein a mixture gas of Ar and O2 (as an ambient gas) and a metal target (chromium in the above case) are used for forming a metal oxide film (e.g., the first layers 16a and 26a shown in FIGS. 2A an 2B) and then the ambient gas is replaced by an Ar gas while using the metal target as it is for forming a metal film (e.g., the second layers 16b and 26b shown in FIGS. 2A and 2B), and (ii) one wherein an ambient gas of Ar and a metal oxide target are used for forming a metal oxide film (e.g., the first layers 16a and 26a) and then the metal oxide target is replaced by a metal target without changing the ambient Ar gas for forming a metal film (e.g., the second layers 16b and 26b).
Further, as a method not using a batch process, it is possible to apply a method using a continuous-type (or load lock-type) sputtering apparatus wherein a substrate is transferred from a first chamber charged with a mixture gas of Ar and O2 for forming a metal oxide film (e.g., the first layers 16a and 26a) to a second chamber partitioned with a gate valve by the first chamber and charged with an Ar gas for forming a metal film (e.g., the second layers 16b and 26b).
The thus formed metal oxide and metal films constituting a lamination structure are then subjected to patterning through a photolithographic process to form a patterned masking film having the lamination structure.
However, the above-described masking films 16 and 26 prepared in the above manner were accompanied with several problems due to their lamination structures.
More specifically, it was difficult to design a lamination structure capable of keeping a balance of a decreased degree of the external light reflection (i.e., a decreased reflectance) and an improvement in light-interrupting property in the case of the masking films including the above-described combinations of the metal oxide film and the metal film. Further, in the conventional lamination structure of the masking film as described above, the metal oxide film and the metal film showed different etching degrees at the time of patterning by the photolithographic process, thus causing uneven (stepwise) side surfaces or a stepwise difference in width with respect to the metal and metal oxide films (i.e., a wider metal oxide film and a narrower metal film) to deteriorate a display quality of the liquid crystal panel P. In the case of using a sputtering target of a metal oxide, there arises a problem with respect to mass production, such as a slow sputtering rate and a crack in (or breakage of) the target. Further, in case where the continuous-type sputtering apparatus is used, the apparatus is accompanied with problems, such as an expensive apparatus and complicated film-forming steps, thus resulting in an increase in production cost.
In order to lower a degree of the external light reflection, it is necessary to appropriately control an oxygen content of a metal oxide film used so as to provide the metal oxide film with an extinction coefficient within an appropriate range in a film-forming step. For example, however, chromium (Cr) has a very high activity with respect to oxygen, so that it is difficult to appropriately control the extinction coefficient range vary depending on a resultant oxygen content, thus failing to provide a color display apparatus exhibiting a good display quality. As a result, a yield of the product is lowered to increase production cost.
There have been also proposed processes for forming a masking film including: one wherein a dyeable synthetic resin is patterned and then dyed with a black dye and one wherein black ink coated through a printing process is subjected to patterning.
In these processes, however, a sufficient light-interrupting (masking) property cannot be ensured in some cases when a thin film is formed. Further, in the latter process, accuracy in patterning or registration is liable to be lowered.
An object of the present invention is to provide a color display apparatus with a high quality and a high accuracy.
Another object of the present invention is to provide a color display apparatus capable of suppressing a stepwise defect due to a difference in etching degree to attain a high quality and a high accuracy.
Another object of the present invention is to provide a color display apparatus capable of lowering its production cost by reducing a production time.
Another object of the present invention is to provide a color display apparatus capable of simplifying production steps.
Another object of the present invention is to provide a color display apparatus capable of decreasing a degree of external-light reflection to improve a display quality.
Another object of the present invention is to provide a color display apparatus capable of preventing an undesired color mixing to attain an excellent display quality.
Another object of the present invention is to provide a color display apparatus not causing a lowering in image quality resulting from stray light.
Another object of the present invention is to provide a color display apparatus capable of preventing a low film-forming rate and a breakage of a target during a step of forming a masking member to allow mass production.
Another object of the present invention is to provide a color display apparatus capable of reducing production cost through an improvement in a production yield.
Another object of the present invention is to provide a color display apparatus capable of reducing a cost of disposal of waste solvent (solution).
A further object of the present invention is to provide a process for producing the above-described color display apparatus.
According to a first aspect of the present invention, there is provided a display apparatus, comprising:
a planar optical modulation device comprising a transparent substrate and a plurality of pixels disposed thereon so as to be each capable of optical modulation thereat, and
a masking member disposed on the transparent substrate and with spacings,
wherein the making member includes a layer of a metal compound containing C, O and a metal element (herein, including a single metal and an alloy).
The display apparatus may preferably further include a plurality of color filters disposed in alignment with the pixels and on the transparent substrate at the spacings of the masking member. The masking member may comprise a first portion located at a first boundary between the transparent substrate and the masking member and having a first refractive index and a first extinction coefficient, and a second portion located at a second boundary opposite to the first boundary and having a second refractive index larger than the first refractive index and a second extinction coefficient larger than the first extinction coefficient. Further, the masking member comprise at least a first layer disposed on the transparent substrate and a second layer disposed on the first layer, wherein the first layer has a refractive index n1 and an extinction coefficient k1 and the second layer has a refractive index n2 and an extinction coefficient k2 satisfying the following relationships: n1 less than n2 and k1 less than k2. In this case, the masking layer may further comprise a third layer disposed on the second layer and having a refractive index n3 and an extinction coefficient k3, wherein the refractive index n1 is equal to or smaller than the refractive index n2 or n3 and the extinction coefficient k1 is equal to or smaller than the extinction coefficient k2 or k3. The above refractive indices n1, n2 and n3 and the extinction coefficients k1, k2 and k3 may preferably satisfy the following relationships: n1 less than n2, n3 less than n2, k1 less than k2 and k3 less than k2. The masking member may have a refractive index and a extinction coefficient respectively increase continuously with an increasing distance from the transparent substrate. In the above display apparatus, the metal element may comprise Mo, preferably Mo and Ta.
The above-mentioned display apparatus may preferably further comprise another transparent substrate disposed opposite to and in substantially parallel with the transparent substrate, and a liquid crystal disposed between the transparent substrates. The display apparatus may further comprise an illumination means disposed on the back side of another transparent substrate.
According to a second aspect of the present invention, there is provided a display apparatus, comprising:
a planar optical modulation device comprising a transparent substrate and a plurality of pixels disposed thereon so as to be each capable of optical modulation thereat, and
a masking member disposed with spacings and including a first layer disposed on the transparent substrate, a second layer disposed on the first layer and a third layer disposed on the second layer,
wherein each of the first to third layers comprises a layer of a metal compound containing a metal element and at least one of C and O.
In the above type of display apparatus, the apparatus may preferably further comprise a plurality of color filters disposed in alignment with the pixels and on the transparent substrate at the spacings of the masking member. Each of the first to third layers may contain at least one of C and O, preferably both C and O.
In the above apparatus (second aspect of the invention), the first layer may preferably have a refractive index n1 and an extinction coefficient k1, the second layer has a refractive index n2 and an extinction coefficient k2, and the third layer has a refractive index n3 and an extinction coefficient k3; wherein the refractive index n1 is equal to or smaller than the refractive index n2 or n3 and the extinction coefficient k1 is equal to or smaller than the extinction coefficient k2 or k3. In this case, the refractive indices n1, n2 and n3 and the extinction coefficients k1, k2 and k3 satisfy the following relationships:
n2 less than n1 less than n3 and k2 less than k1 less than k3.
In the above apparatus (second aspect), the first layer may contain Mo, preferably Mo and Ta, and the second layer may contain Al or Si. The apparatus may preferably further comprise another transparent substrate disposed opposite to and substantially parallel with the transparent substrate, and a liquid crystal disposed between the transparent substrates. The apparatus may further comprise an illumination means disposed on the back side of the another transparent substrate.
In the apparatus of the first aspect of the invention, the masking member may include a first layer disposed on the transparent substrate and comprising a metal compound containing C, O and a metal element and a second layer disposed on the first layer and comprising a metal element. In the display apparatus of this type, the first layer may be controlled to have a carbon content and an oxygen content each being substantially uniform in a direction of its thickness or each decreasing from the transparent substrate side toward the second layer side in a direction of its thickness. Further, the masking member may further comprise a third layer disposed on the second layer and containing C, O and a metal element, which may be selected from the group consisting of Mo, Ti, Cr, Al, Ta and W. In this case, the third layer may preferably contain Mo. Similarly, the first layer may contain a metal element selected from the group consisting of Mo, Ti, Cr, Al, Ta and W and the second layer may contain a metal element selected from the group consisting of Mo, Ti, Cr, Al, Ta and W. In this instance, the first layer may preferably contain Mo and the second layer may preferably contain Mo. Further, the first layer may desirably have an extinction coefficient k satisfying the following relationship: 0.2xe2x89xa6kxe2x89xa61.0. The apparatus may further comprise another transparent substrate disposed opposite to and substantially parallel with the transparent substrate, and a liquid crystal disposed between the transparent substrates. The apparatus may also comprise an illumination means disposed on the back side of the another transparent substrate.
The present invention further provides a process for producing a display apparatus of the type comprising a planar optical modulation device comprising a transparent substrate and a plurality of pixels disposed thereon so as to be each capable of optical modulation thereat, and a masking member disposed on the transparent substrate and with spacings; wherein the process comprises: a sputtering step wherein a layer of a metal compound comprising C, O and a metal element is formed on a transparent substrate by sputtering with an ambient gas including C, O and Ar.
The present invention further provides a process for producing a display apparatus of the type comprising a planar optical modulation device comprising a transparent substrate and a plurality of pixels disposed thereon so as to be each capable of optical modulation thereat, and a masking member disposed with spacings and including a first layer, a second layer and a third layer; wherein the process comprises:
forming the first layer on a transparent substrate by sputtering,
forming the second layer on the first layer by sputtering, and
forming the third layer on the second layer by sputtering;
wherein the first to third layers are respectively formed by using an ambient gas comprising Ar and at least one of C and O,
the first and third layers are respectively formed by using a target of a first metal element, and
the second layer is formed by using a target of a second metal element.
In the latter process described above, the first metal element may preferably comprise Mo and the second metal element may preferably comprise Al or Si. In this case, the first metal element may particularly preferably be an alloy of Mo and Ta. Further, the ambient gas may preferably comprise a mixture gas of Ar and CO2 in the steps for forming the first to third layers.
In the former and the latter processes described above, the sputtering may be performed by changing a sputtering power so as to provide an objective layer with a prescribed refractive index and a prescribed extinction coefficient.
The present invention further provides a process for producing a display apparatus of the type comprising a planar optical modulation device comprising a transparent substrate and a plurality of pixels disposed thereon so as to be each capable of optical modulation thereat, and a masking member disposed with spacings and including a first layer and a second layer; wherein the process comprises the steps of:
forming the first layer on the transparent substrate by sputtering with a target comprising a metal element selected from the group consisting of Ti, Cr, Al, Ta, Mo and W and with an ambient gas comprising a mixture gas of Ar and CO2, and
forming the second layer on the first layer by sputtering with a target comprising a metal element selected from the group consisting of Ti, Cr, Al, Ta, Mo and W and with an ambient gas of Ar.
These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings.